5G radio access network (RAN) architects actively seek to augment mobile systems with inexpensive spectrum portions, in order to boost network capacity and meet growing user demand in a cost-effective manner. License-exempt 5-GHz Unlicensed National Information Infrastructure (U-NII) channels, currently exploited almost exclusively by Wi-Fi deployments, are of particular interest to the 3rd Generation Partnership Project (3GPP) community, who is pursuing Long-Term Evolution (LTE) standardization in the unlicensed arena (U-LTE). However, the substantial differences between incumbent Wi-Fi, which employs a listen-before-talk (LBT) contention-based multiplexing protocol (CSMA/CA), and LTE, which is inherently a scheduled paradigm, makes the design of U-LTE channel access protocols particularly challenging.